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344                          FOUR-FINGERED WHALES                         CHAP,
The pectoral fin of Whales exists in two forms. In the
Tootlied Whales it is shorter and rounder; in the Whalebone
"Whales longer and narrower. Structural differences accompany
these outward dissimilarities. In the first-named group the
humeras and the beginning of the radius and ulna are within the
body, and do not form a part of the fin. In the Whalebone
Whales, on the other hand, the fin contains all the bones of the
fore-limb. Another remarkable contrast between the hand in
the two groups of Whales is that while the Toothed Whales have
five fingers, thus justifying the prevailing opinion that they are
the more primitive of the two groups, the Whalebone Whales have
only four fingers. Actually the Sight Whale, Balaena, seems to
have five fingers; and, indeed, the fact that it has, is often used to
distinguish it from the Humpback, which has undoubtedly only four.
But a careful consideration of the state of affairs which prevails in
the foetus of Balaenoptera dispels this idea. Between what are
apparently the second and third fingers, a rudimentary finger,
consisting of four phalanges, appears. This is not produced, as is
an additional finger found in the White Whale or Beluga, by a
splitting of a finger. Accordingly the four-fingered condition of
the Whalebone Whales is produced by the dropping out of a finger
in the middle of the series,—a very remarkable fact. When
fingers disappear, as, for intsance,, in the Horse, etc., it is at the
two ends of the series that the digits vanish. If this view of
Professor KilkenthaFsI be accepted, it follows that the pre-
sumed thumb of the Eight Whale is what has been termed the
The hand of the Whales, like those of some other aquatic
creatures, e.g. the reptile Ichthyosaurus, has a larger number of
phalanges than have terrestrial animals. The result of this is,
of course, to increase the length of the fin and its utility as a
paddle. It is commonly not all the fingers that have developed
this great number of accessory phalanges. Rudimentary nails
have been found upon the Cetacean hand; but in no case are
they functionally developed. In the Manatees we have the
disappearance of the nails still imperfectly accomplished. In
M latirostTi® there are nails; these have vanished, apart from
possible traces to be seen with a microscope, in J£ innnynis*
A very characteristic feature of certain Whales are the furrows
an JWaU&iere, Jena, 1889-9S.